Active illumination 3d zonal imaging system

ABSTRACT

An active illumination range camera comprising illumination and imaging systems that is operable to provide a range image of a scene in the imaging system&#39;s field of view (FOV) by partitioning the range camera FOV into sub-FOVs, and controlling the illumination and imaging systems to sequentially illuminate and image portions of the scene located in the respective sub-FOVs.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims priority toU.S. patent application Ser. No. 15/646,124, entitled “ACTIVEILLUMINATION 3D ZONAL IMAGING SYSTEM,” filed on Jul. 11, 2017, thedisclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

An active illumination range camera comprises an illumination systemthat it controls to transmit light to illuminate features in a scenethat the camera images, and a photosensor having pixels on which thecamera registers light that the features reflect from the transmittedlight back to the camera. The range camera processes reflected lightfrom the features that pixels in the photosensor register to providemeasures of distances to the features in the scene. In a time of flight(TOF) range camera the camera processes the registered reflected lightfrom a feature to determine a round trip flight time of light from thecamera to the feature and back to the camera. The TOF range cameradetermines a measure of a distance of the feature from the camera basedon the round-trip flight time and the speed of light. A TOF range cameramay be a gated TOF (GT-TOF) range camera or a “continuous wave” TOF(CW-TOF) range camera. In an active illumination stereo range camera,the camera provides measures of distances to features in the scene bydetermining binocular disparity for the features responsive to reflectedlight from the features that the camera registers. The cameratriangulates the features based on their respective disparities todetermine measures of distances to the features. A range camera mayprovide measures of distances to features in a scene that the cameraimages in an image of the scene referred to as range image.

SUMMARY

An aspect of an embodiment of the disclosure relates to providing anactive illumination range camera comprising illumination and imagingsystems that is operable to provide a range image of a scene in theimaging system's field of view (FOV) by partitioning the range cameraFOV into sub-FOVs, and controlling the illumination and imaging systemsin synchronization to sequentially illuminate and image portions of thescene located in the respective sub-FOVs. Hereinafter, a sub-FOV may bereferred to as a zone, and illuminating a portion of a scene located ina given zone with light from the illumination system may be referred toas illuminating the given zone. Imaging a portion of a scene located inthe given zone may be referred to as imaging the given zone. In anembodiment, illuminating a given zone may comprise controlling theillumination system so that light in a field of illumination (FOI) ofthe illumination system illuminates substantially only that portion ofthe scene located in the given zone. Imaging a given zone may compriseoperating a photosensor of the camera so that substantially only pixelson which features in the given zone are imaged register light to acquiredata for providing a range image of the scene.

By sequentially illuminating and imaging zones to provide a range imageof the scene, the range camera may operate to acquire the range image atintensities of illumination greater than intensities practicallyavailable when operating to simultaneously illuminate and image theentirety of the FOV. Furthermore, since a zone is a portion of andtherefor narrower than, the full FOV of the camera, acquiring the rangeimage by imaging zones operates to mitigate deleterious effects ofmultipath light.

In an embodiment the active illumination range camera, hereinafter alsoreferred to as a zonal range camera, may comprise any one or anycombination of more than one of a continuous wave CW-TOF zonal rangecamera, a gated TOF zonal range camera, and/or a stereo zonal rangecamera.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF FIGURES

Non-limiting examples of embodiments of the disclosure are describedbelow with reference to figures attached hereto that are listedfollowing this paragraph. Identical features that appear in more thanone figure are generally labeled with a same label in all the figures inwhich they appear. A label labeling an icon representing a given featureof an embodiment of the disclosure in a figure may be used to referencethe given feature. Dimensions of features shown in the figures arechosen for convenience and clarity of presentation and are notnecessarily shown to scale.

FIGS. 1A-1D schematically illustrate an active illumination zonal rangecamera imaging a scene by sequentially illuminating and imagingdifferent zones of the scene, in accordance with an embodiment of thedisclosure;

FIGS. 2A-2C show flow diagrams of different zonal imaging procedures inaccordance with which a continuous wave time of flight, a CW-TOF, zonalrange camera may execute to acquire a range image of a scene, inaccordance with an embodiment of the disclosure; and

FIG. 3A-3B schematically shows a photosensor of a CW-TOF zonal rangecamera and details of pixels in the photosensor configured to operate ina zonal imaging mode to acquire a range image of a scene, in accordancewith an embodiment of the disclosure.

DETAILED DESCRIPTION

In the detailed discussion below features of a zonal range camera,operating to acquire a range image of a scene in accordance with anembodiment of the disclosure are discussed with reference to FIGS.1A-1D. Three different procedures by which a CW-TOF zonal range cameramay operate in accordance with an embodiment of the disclosure toacquire a range image of a scene are discussed with respect to flowdiagrams given in FIGS. 2A-2C. Operation of a photosensor and pixels ina CW-TOF zonal range camera are schematically illustrated and discussedwith reference to FIG. 3.

In the discussion, unless otherwise stated, adjectives such as“substantially” and “about” modifying a condition or relationshipcharacteristic of a feature or features of an embodiment of thedisclosure, are understood to mean that the condition or characteristicis defined to within tolerances that are acceptable for operation of theembodiment for an application for which it is intended. Unless otherwiseindicated, the word “or” in the description and claims is considered tobe the inclusive “or” rather than the exclusive or, and indicates atleast one of, or any combination of items it conjoins.

FIGS. 1A-1D schematically show an active illumination, zonal rangecamera 20 imaging a scene 80 in accordance with an embodiment of thedisclosure. Zonal range camera 20 comprises an imaging system 30, anillumination system 60, and a controller 22 configured to control theilluminating and imaging systems.

Controller 22 may comprise any electronic and/or optical processingand/or control circuitry, to provide and enable functionalities that thecontroller may require to support its operations in controlling theilluminating and imaging systems. By way of example, controller 22 maycomprise any one, or any combination of more than one of, amicroprocessor, an application specific circuit (ASIC), fieldprogrammable array (FPGA) and/or system on a chip (SOC). Controller 22may control and/or have access to a memory (not shown) which maycomprise any electronic and/or optical circuitry suitable for storingdata and/or computer executable instructions and may, by way of example,comprise any one or any combination of more than one of a flash memory,random access memory (RAM), read only memory (ROM), and/or erasableprogrammable read-only memory (EPROM).

Imaging system 30 optionally comprises a photosensor 32 having lightsensitive pixels 34 shown in an enlarged image of the photosensor in aninset 91, and an optical system schematically represented by a lens 36.Scene 80 is located in a FOV 50 of range camera 20 shown in FIG. 1A. TheFOV is determined by imaging system 30 and outlined by bounding lineslabeled with the reference label, 50, of the FOV. Optical system 36operates to receive light reflected by features (features not shown) inscene 80 from light transmitted by illumination system 60 and image thereceived light on photosensor 32 to acquire data for a range image ofthe scene. In an embodiment, each pixel 34 may selectively be controlledindependently of other pixels 34 to be turned ON or OFF for an exposureperiod to register light incident on the pixel when ON and provide ameasurement of the registered light.

A pixel in a camera photosensor registers incident light from a featurein a scene that optics in the camera focuses on the pixel byaccumulating, also referred to as integrating, negative or positiveelectric charge provided respectively by electrons or holes fromelectron-hole pairs that the incident light generates in the pixelduring an exposure period of the pixel. The charge provided by electronsor holes from electron-hole pairs may be referred to generically as“photocharge”. Camera photosensors are typically configured so thattheir pixels accumulate electrons, conventionally also referred to as“photoelectrons”, and thereby negative photocharge originating fromelectron-hole pairs, rather than holes and thereby positive photochargeto register incident light.

Converting an amount of photocharge that a pixel in the photosensoraccumulates, or integrates, responsive to incident light from the sceneto a voltage, hereinafter also referred to as a readout voltage,provides a measurement of an amount of the incident light that the pixelregisters. Providing the readout voltage may involve temporarily storingthe accumulated photocharge in a storage capacitor of the pixel andtransferring the photocharge to a readout capacitor for conversion ofthe stored photocharge to a readout voltage. Determining a value for areadout voltage of a pixel may be referred to as reading the pixel.Reading the pixels in the photosensor or a portion of the photosensormay be referred to as reading the photosensor or portion of thephotosensor. A collection of values of substantially all the readoutvoltages, or function of the readout voltages, comprised in thephotosensor or portion of the photosensor is referred to as a frame ofthe photosensor or portion thereof and may be used to provide an imageof the scene or portion thereof.

Illumination system 60 may comprise a light source 61, an optical systemrepresented by a lens 62, and a beam steerer 63 that controller 22 maycontrol to produce and configure a desired field of illumination (FOI)of light and direct the FOI in a desired direction to illuminatedifferent portions of scene 80 within FOV 50 of range camera 20. InFIGS. 1A-1D controller 22 is shown by way of example, controllingillumination system 60 to generate and direct a FOI 70 schematicallyshown as frustum shaped and outlined by bounding lines labeled with thereference label 70 of the FOI.

Light source 61 optionally comprises at least one light producingelement such as a laser or light emitting diode (LED). Optionally, lightsource 61 comprises an array 65 of light producing elements 66, such asVCSELs (vertical cavity surface emitting lasers) schematically shown inan inset 92 that are individually controllable to shape a beam of light,and thereby FOI 70, from the light source. In an embodiment, lightproducing elements 66 may be turned ON and OFF independently of eachother to change a shape and/or direction of FOI 70 provided byillumination system 60. Light source 61 is configured for generating,optionally IR (infrared) light, suitable for use with a type of rangecamera to which zonal range camera 20 may belong. For example, if rangecamera 20 operates as a stereo range camera, light source 61 may beconfigured to illuminate a scene imaged by the camera with structuredlight, such as, optionally, a textured light pattern. If range camera 20operates as a TOF range camera, light source 61 may be controllable togenerate temporally modulated light for illuminating a scene that isimaged by the camera. If operating as a gated, GT-TOF, range camera,light source 61 of range camera 20 may be configured to generate a trainof discrete, short light pulses for illuminating a scene. The GT-TOFrange camera determines distances to features in a scene that the cameraimages based on round trip flight times of the discrete light pulsesfrom the camera to the features and back to the camera. If range camera20 operates as a continuous wave, CW-TOF, range camera, light source 61may be configured to generate a continuous wave of time modulated lightfor illuminating a scene. The CW-TOF camera determines distances tofeatures in the scene based on phase shifts of light that the featuresreflect from the transmitted light relative to the modulation of thetransmitted light.

Optical system 62 of illumination system 60 may comprise a collimatinglens and diffuser (not shown) that receives and shapes light from lightsource 61 to provide a desired FOI, such as FOI 70, and transmits thelight to FOI steerer 63. FOI beam steerer 63 is controllable toselectively steer the light that it receives so that it illuminates adesired region of a scene imaged by zonal range camera 20. FOI beamsteerer 63 may comprise any one or any combination of more than one, ofvarious light steering elements such as, liquid crystal gratings,electrowetting prisms, conventional micro-sized mirrors, and/ormicromirror arrays. By way of example, FOI beam steerer 63 isschematically shown as a mirror in FIG. 1A.

In an embodiment of the disclosure to image a scene, such as scene 80,controller 22 partitions FOV 50 into a plurality of zones and controlsillumination system 60 to configure and direct the illumination system'sFOI 70 to sequentially illuminate the zones, one zone of the pluralityof zones at a time. While a given zone is illuminated by lighttransmitted by illumination system 60 in FOI 70, controller 22 turns ONpixels 34 in photosensor 32 to register light reflected from thetransmitted light by features of scene 80 located in the given zone foruse in determining distances to the features and providing a range imageof scene 80. Pixels 34 that image features of scene 80 which are locatedoutside of the given zone may be turned OFF so that they do not registerlight for use in determining distances to features in scene 80.

A region of photosensor 32 comprising pixels 34 that are turned ON foran exposure period to register light from features in a given zoneilluminated by FOI 70 may be referred to as an active or an activatedregion of the photosensor and turning ON pixels 34 in a region ofphotosensor 32 may be referred to as activating the region. A region ofphotosensor 32 comprising pixels 34 that are turned OFF may be referredto as an inactive or an inactivated region of the photosensor andturning OFF pixels in a region of photosensor 32 may be referred to asinactivating the region. It is noted that referring to a pixel as turnedON refers to the pixel being operated to accumulate photocharge for usein providing a range image of a scene responsive to light transmitted byillumination system 60 in FOI 70 during an exposure period of the pixel.Referring to a pixel as being turned OFF and inactive refers to thepixel being operated so that it does not accumulate photochargeresponsive to light transmitted by illumination system 60 for use inproviding a range image. While OFF, however, a pixel may not be totallyinactive and may for example be operated to transfer photochargeaccumulated during an exposure period to a storage capacitor, maintainstorage of transferred photocharge in a storage capacitor, or transferphotocharge to a readout capacitor.

By way of example, FIG. 1A schematically shows FOV 50 of zonal rangecamera 20 partitioned by controller 22 into a plurality of optionallyfour zones. Each zone intersects scene 80 in a different respectiveregion, 81, 82, 83, or 84 of scene 22 and may be identified by, and bereferred to by the numeral labeling its intersection region. Light fromfeatures of scene 80 located in zones 81, 82, 83, or 84 are imaged byimaging system 30 on pixels 34 in regions 32-81, 32-82, 32-83, and 32-84respectively of photosensor 30.

In FIG. 1A controller 22 is shown controlling illumination system 60 toconfigure and direct FOI 70 to illuminate zone 81 and imaging system 30to turn ON pixels 34 in corresponding region 32-81 of photosensor 30 toactivate the region for an exposure period. Visualization aid lines 101in the figure schematically indicate light from region 81 collected byimaging system 30 and imaged on corresponding region 32-81 ofphotosensor 32. During the exposure period region 32-81 registers lightreflected by features of scene 80 in zone 81 from light transmitted inFOI 70 to acquire data for determining distances to the features. Whileactivating photosensor region 32-81, controller 22 optionally turns OFFpixels 32 in photosensor regions 32-82, 32-83, 32-84 to inactivate theregions. Active region 32-81 is shown shaded to differentiate the activeregion from inactive regions 32-82, 32-83, 32-84 of photosensor 32 whichare shown unshaded.

Following illuminating and registering reflected light from zone 81,controller 22 may control zonal range camera 20 to sequentiallyilluminate and register reflected light from features of scene 80located in zones 82, 83, and 84 as schematically shown in FIGS. 1B, 1Cand 1D respectively. In an embodiment controller 22 may repeatsequentially illuminating and registering light from zones 81-84 untilsufficient data is acquired for features in FOV 50 to provide a rangeimage of scene 80 in accordance with an embodiment. Different proceduresthat zonal range camera 20 operating as a CW-TOF zonal range camera mayperform to acquire a range image of scene 80 are discussed below.

It is noted that whereas in FIGS. 1A-1D FOV 50 is shown, and discussedin the above discussion as partitioned, into four zones, practice ofembodiments of the disclosure are not limited to partitioning an FOV ofa zonal range camera, such as zonal range camera 20, into four zones.Controller 22 may partition a FOV into a number of zones that is more orless than four. It is also noted that whereas in FIG. 1A zones 81-84 areschematically indicated as characterized by rectangular cross sectionsthat subtend equal solid angles at illumination system 60, practice ofan embodiment of the disclosure is not limited to zones havingrectangular cross sections or equal solid angles. Different zones maysubtend different solid angles at illumination system 60 and a zone mayhave a cross section that is not rectangular. A zone may, for examplehave a circular, hexagonal, or an irregular cross section.

In an embodiment controller 22 may be configured to determine a numberof zones into which to partition FOV 50 based on reflectance of featuresin scene 80 for light transmitted by illumination system 60 andintensity of illumination available from illumination system 60. Forexample, a scene with low reflectance features may require illuminationby light having relatively high intensity to provide a satisfactoryrange image of the scene. For such a situation controller 22 maypartition scene 80 into a relatively large number of relatively smallzones so that illumination system 60 may be controlled to illuminateeach zone with light characterized by relatively high intensity. In anembodiment controller 22 may control illumination system 60 toilluminate different zones with different intensity light. For example,controller 22 may control illumination system 60 to illuminate highlyreflective zones with lesser intensity light than poorly reflectivezones and poorly reflective zones with higher intensity light.Additionally or alternatively, controller 22 may differentially modulatesensitivity of pixels in photosensor 32 to light so that pixels on whichoptical system 36 images features from different zones of a sceneregister light during exposure periods having different durations. Forexample, pixels on which features from highly reflective zones areimaged may be controlled to register light during exposure periods thatare shorter than the exposure periods of pixels on which features frompoorly reflective zones are imaged.

FIG. 2A shows a flow diagram 200 of a procedure by which CW-TOF zonalrange camera 20 operating as a CW-TOF zonal range camera may determinedistances to features in a scene, such as by way of example scene 80,and provide a range image of the scene

In a block 201 controller 22 optionally determines a number N_(z) ofzones, Z(n_(z)), 1≤n_(z)≤N_(z), into which to partition FOV 50, a numberN_(f) of frequencies, F(n_(f)), 1≤n_(f)≤N_(f) of light at which toilluminate scene 80, and for each frequency a number N_(p) of samplingoffset phases P(n_(p)), 1≤n_(f)≤N_(f) at which to acquire data forproviding a range image of the scene. Optionally in a block 203 thecontroller zeros counting variables n_(z), n_(f), n_(p) that correspondrespectively to N_(z), N_(f), and N_(p). In blocks 205, 207, and 209respectively, the controller increases counting variables n_(z), n_(f),n_(p) by 1, and sets n_(z)=(n_(z)+1), n_(f)=(n_(f)+1), andn_(p)=(n_(p)+1).

Optionally, in a block 211, controller 22 controls illumination system60 to illuminate zone Z(n_(z)) with light at a frequency F(n_(f)). And,optionally, in a block 213 the controller turns ON pixels 34 in a regionPR(n_(z)) of photosensor 32 on which imaging system 30 images light fromfeatures in zone Z(n_(z)) to operate at an offset phase P(n_(p)) andactivate the region for an exposure period. During the exposure periodpixels 34 in activated region PR(n_(z)) accumulate for frequencyF(n_(f)) and offset phase P(n_(p)) photocharge generated by light thatthe features in zone Z(n_(z)) reflect back to CW-TOF zonal camera 22from light transmitted by illumination system 60 to illuminate zoneZ(n_(z)). In a block 215 controller 22 reads pixels 34 in photosensor 32to acquire data at frequency F(n_(f)) and offset phase P(n_(p)) fordetermining a range image for scene 80.

In a decision block 217 controller 22 determines if counting variablen_(p) is equal to the maximum N_(p), and if n_(p) is not equal to N_(p),returns to block 209 to increase n_(p) by 1 and again proceeds throughactions in block 211 to 217. If on the other hand in block 217controller 22 determines that n_(p)=N_(p) the controller proceeds to adecision block 219.

In decision block 219, controller 22 determines if counting variablen_(f) is equal to its maximum N_(f), and if n_(f) is not equal to N_(f),returns to block 207 to increase n_(f) by 1 and again proceed throughactions in block 207 to 219. If on the other hand in block 217controller 22 determines that n_(f)=N_(f) CW-TOF zonal camera 20 hasacquired data advantageous for determining distances to features ofscene 80 in zone Z(n_(z)) and the controller proceeds optionally to ablock 221. In block 221 the controller uses the acquired data todetermine distances to features in zone Z(n_(z)) and may proceed to adecision block 223.

In decision block 223, controller 22 determines if counting variablen_(z) is equal to its maximum N_(z), and if n_(z) is not equal to N_(z),returns to block 205 to increase n_(z) by 1 and again proceed throughactions in block 207 to 223. If on the other hand in block 223controller 22 determines that n_(z)=N_(z), the CW-TOF camera 20 hasacquired data for each of frequencies F(n_(f)), 1≤n_(f)≤N_(f), andoffset phases P(n_(p)) 1≤n_(p)≤N_(p), for all N_(z) zones into which FOV50 is partitioned, and determined distances to features of scene 80 inthe N_(z) zones. The controller may proceed to a block 225 and combinedistances determined for features in all of the zones to provide a rangeimage for features in FOV 50 and thereby a range image for scene 80.

FIG. 2B shows a flow diagram 200 for another procedure by which CW-TOFzonal range camera 20 operating as a CW-TOF zonal range camera mayprovide a range image of scene 80.

Blocks 301 and 302 of procedure 300 are identical to blocks 201 and 202of procedure 200, and in blocks 305, 307, and 309 controller 22 setsn_(f)=(n_(f)+1), n_(p)=(n_(p)+1), and n_(z)=(n_(z)+1). Optionally, in ablock 311, controller 22 controls illumination system 60 to illuminatezone Z(n_(z)) with light at a frequency F(n_(f)). And in a block 313,for frequency F(n_(f)) and offset phase P(n_(p)), the controlleractivates photosensor region PR(n_(z)) to accumulate photochargegenerated by light reflected back to CW-TOF zonal camera 22 from lighttransmitted by illumination system 60 to illuminate zone Z(n_(z)) byfeatures in the zone. In a block 315 controller 22 controls pixels 34 inPR(n_(z)) to store photocharge that the pixels respectively accumulatedin storage capacitors of the pixels.

In a decision block 317 controller 22 determines if counting variablen_(z) is equal to the maximum N_(z). If n_(z) is not equal to N_(z),controller 22 returns to block 319 to read and reset all photosensorregions PR(n_(z)) and proceed to a decision block 321 to determine ifn_(p) is equal to the maximum N_(p). If n_(p) is not equal to N_(p) thecontroller returns to block 307 to increase n_(p) by 1 and again proceedto execute actions in blocks 309 to 321, otherwise controller 22 mayproceed to a decision block 323 to determine if n_(f) is equal to N_(f).If n_(f) is not equal to N_(f) controller 22 returns to block 305 toincrease n_(f) by 1 and again proceed to execute actions in blocks 307to 323. If on the other hand n_(f) is equal to N_(f) CW-TOF camera 20has acquired sufficient data to provide a range image for FOV 50 andscene 80, and in a block 325 processes the data to provide the rangeimage.

FIG. 2C shows a flow diagram 400 for yet another procedure by whichzonal range camera 20 operating as a CW-TOF zonal range camera mayoperate to provide a range image of scene 80.

Blocks 401 and 402 of procedure 400 are identical to blocks 201 and 202of procedure 200 and in blocks 405, 407, and 409 controller 22 setsn_(f)=(n_(f)+1), n_(p)=(n_(p)+1), and n_(z)=(n_(z)+1). Optionally, in ablock 411, controller 22 controls illumination system 60 to illuminatezone Z(n_(z)) with light at a frequency F(n_(f)). And in a block 413,for frequency F(n_(f)) and offset phase P(n_(p)), the controlleractivates photosensor region PR(n_(z)) to accumulate photochargegenerated by light reflected by features in zone Z(n_(z)) back to CW-TOFzonal camera 22 from light transmitted by illumination system 60 toilluminate zone Z(n_(z)). In a block 415 controller 22 reads and resetspixels 34 in PR(n_(z)).

In a decision block 417 controller 22 determines if counting variablen_(z) is equal to N_(z). If n_(z) is not equal to N_(z), controller 22returns to block 409 to increase n_(z) by 1 and again proceed to executeactions in blocks 409 to 417. If on the other hand n_(z) is equal toN_(z), the controller proceeds to a decision block 419 to determine ifn_(p) is equal to N_(p). If n_(p) is not equal to N_(p) the controllerreturns to block 407 to increase n_(p) by 1 and again proceed to executeactions in blocks 409 to 419, otherwise controller 22 may proceed to adecision block 421 to determine if n_(f) is equal to N_(f). If n_(f) isnot equal to N_(f) controller 22 returns to block 405 to increase n_(f)by 1 and again proceed to execute actions in blocks 407 to 421. If onthe other hand n_(f) is equal to N_(f), CW-TOF camera 20 has acquired adesired amount of data to provide a range image for FOV 50 and scene 80,and in a block 423 processes the acquired data to provide the rangeimage.

FIG. 3A schematically shows photosensor 32 having pixels 34 configuredfor operation in a CW-TOF zonal range camera such as range camera 20 inaccordance with an embodiment of the disclosure. An enlarged, schematictop view of a pixel 34 showing details of the pixel construction isshown in an inset 93.

Pixel 34 may be implemented in front or back side illumination andcomprise two, optionally parallel structures 500 and 600, eachoptionally independently controllable to accumulate photochargegenerated by incident light and provide a readout voltage as a measureof the accumulated photocharge. Structure 500 optionally comprises aphotosensitive region 501, a reset node 502, a charge storage node 503,and a readout node 504, formed in a semiconductor substrate 499 on whichphotosensor 32 is formed. Photosensitive region 501, reset node 502,charge storage node 503 and readout node 504 are overlaid by controlelectrodes 511, 512, 513, and 514 respectively. Electrode 511 controlssensitivity of photosensitive region 501 to light incident on theregion. Gate electrodes 521, 522, and 523 are located between controlelectrodes 511 and 512, 511 and 513, and 513 and 514 respectively.Photosensitive region 501 comprises a photodiode or photogate (notshown), in which photocharge, optionally photoelectrons may be generatedand accumulated responsive to light incident on the photosensitiveregion. Control electrode 511 overlying photosensitive region 501 may betransparent to light for which photosensitive region 503 is intended toaccumulate photoelectrons and may for example be formed frompolysilicon. Control electrodes 512, 513, and 514, and transfer gateelectrodes 521, 522, and 523 may be substantially opaque to light thatmay generate photocharge in the nodes and regions under the electrodes.The opaque electrodes may for example be formed from salicidedpolysilicon. Readout node 504 is connected to an output circuitry (notshown) of photosensor 32 configured to readout photosensor 32. An arrow530 represents a connection of readout node 504 to the output circuit.

Controller 22 applies a time varying voltage, V_(F), typically modulatedat a frequency of light that illumination system transmits, to controlelectrode 511 to control sensitivity of photosensitive region 501 toincident light. Controller 22 electrifies control electrode 512 with adrain voltage V_(dd), and electrifies electrode 513 with a voltage V_(C)that controls capacity of charge storage node 503 to store photochargegenerated by photosensitive region 501. Controller 22 applies a voltageV_(G) to gate electrode 521 to connect photosensitive region 501 toV_(dd) node 502 and a bias voltage V_(B) to gate electrode 522 totransfer photocharge from photosensitive region 501 to storage node 503.The controller transfers charge from storage region 503 to readout node504 by applying a voltage V_(T) to gate electrode 523.

Accumulation of photoelectrons in photosensitive region 501 and transferof accumulated photoelectrons for storage to charge storage node 503 andfrom storage node 503 to readout node 504 may be controlled by suitablyelectrifying the control and gate electrodes. For example, applying apositive voltage V_(F) to control electrode 511 overlying photosensitiveregion 501 relative to voltages V_(G) and V_(B) applied to gateelectrodes 521 and 522 provides for accumulation of photoelectrons inphotosensitive region 501. Photoelectrons accumulated in photosensitiveregion 501 may be transferred to storage node 503 by electrifyingtransfer gate electrode 522 with V_(B) more positive than voltage V_(F)applied to control electrode 511 overlying photosensitive region 501,and control electrode 513 overlying charge storage node 503 with voltageV_(C) more positive than voltage V_(B) applied to gate electrode 522.Electrifying transfer gate electrode 523 with voltage V_(T) morepositive than voltage V_(C) applied to control electrode 513 and controlelectrode 514 more positive than voltage of transfer gate electrode 523transfers photoelectrons stored in storage node 503 to readout node 504.In the readout node the transferred photoelectrons generate a readoutvoltage for readout and processing by the output circuitry ofphotosensor 32. Reset node 502 may be connected to a reset voltagesource (not shown) and photosensitive region 501 may be reset andemptied of accumulated photoelectrons by electrifying transfer gate 521positive relative to control electrode 511.

Structure 600 is similar to structure 500 and comprises a photosensitiveregion 601, reset node 602, charge storage node 603, and read out node604 overlaid by control electrodes 611, 612, 613, and 614 respectively.Transfer gate electrodes 621, 622, and 623 are located between controlelectrodes 611 and 612, 611 and 613, and 613 and 614 respectively, andreadout node 604 is connected to the output circuitry of photosensor 32by a connection 630.

In an embodiment control electrodes 511 and 611 are electrified viadifferent control lines, because as described below controller 22 mayapply different voltages to the electrodes, and corresponding electrodesother than electrodes 511 and 611 may be electrified via same controllines. By way of example, as schematically shown in FIG. 3A voltagesV_(F) and V*_(F) are respectively provided to electrodes 511 and 611 ina same column of pixels 34 over pixel column control lines labeled V_(F)and V_(F)*. Voltage V_(B) may be applied to gate electrodes 522 and 622in a same column of pixels 34 via a pixel column control line labeledV_(B). Pixel row control lines labeled V_(C), V_(G), and V_(T) mayprovide voltages V_(C), V_(G), and V_(T) to pairs of corresponding gateelectrodes 513 and 613, 521 and 621, and 523 and 623 in a same row ofpixels respectively.

Pixel 34 may be activated by electrifying control and gate electrodes inthe pixel as described above to enable photosensitive regions 501 and601 to accumulate photoelectrons. The pixel may be controlled to storephotoelectrons by electrifying electrodes in the pixels to transferphotoelectrons from photosensitive regions 501 and 601 to storage nodes504 and 604. Pixel 34 may be inactivated by maintaining photosensitiveregions 501 and 601 connected to reset nodes 512 and 612. The pixel maybe readout by transferring photoelectrons stored in storage nodes 503and 603 to readout nodes 504 and 604 respectively from where they may besensed by the output circuitry of photosensor 32.

In an embodiment, for a given offset phase, controller 22 temporallymodulates voltage applied to control electrodes 501 and 601 overlyingphotosensitive regions 501 and 601 at a frequency of modulation of lightthat illumination system 60 transmits to illuminate a scene, such asscene 80 that CW-TOF zonal camera 20 images. Modulation of electrodes501 are 601 may be out of phase by 180° and one of the electrodes 501and 601 may be phase shifted by the offset phase relative to a phase ofmodulation of the illuminating light from the illumination system. Theoutput circuitry may use a difference between readout voltages providedby readout nodes 504 and 604 responsive to photoelectrons accumulated byphotosensitive regions 501 and 601 to determine a distance to a featureimaged on pixel 34 and provide a range image for scene 80.

FIG. 3B schematically illustrates how controller 22 (FIG. 1A-1D) mayelectrify electrodes of pixels 34 in photosensor 32 to activate a region600 of photosensor 32 corresponding to an illuminated zone (not shown)in FOV 50 of CW-TOF zonal camera 20 (FIG. 1A) in accordance with anembodiment of the disclosure. Column control lines are schematicallyrepresented by solid arrows pointing along columns of photosensor 32labeled by the voltages V_(F) and V_(B). Row control lines areschematically represented by dashed arrows pointing along rows ofphotosensor 32 labeled by the voltages they provide V_(G), V_(T), andV_(C). Voltages applied to column control lines V_(F) and V_(B) as afunction of column location are shown in parentheses following thesymbol of the control line. For convenience of presentation and toprevent clutter column control lines V_(F) and V*_(F) shown in FIG. 3Aare represented in FIG. 3B by V_(F). As noted above, voltages V_(F) andV*_(F) are time varying voltages modulated out of phase by 180° at afrequency equal to a frequency at which illumination system 60 modulateslight that it transmits to illuminate a scene that CW-TOF zonal camera20 images. For columns of pixels for which V_(F) and V*_(F) vary betweensame maximum and minimum voltages the maximum and minimum voltages areshown separated by a hyphen in parentheses following the symbol V_(F)labeling the control line. For example for columns of pixels thattraverse activated region 600 of photosensor 32, the column pixelcontrol lines V_(F) show a voltage range (1-3.3) to indicate that bothV_(F) and V*_(F) vary between 1 volt and 3.3. For pixel control linesV_(F) for which V_(F) and V*_(F) have different ranges the ranges areshown separated by a slash “/” with the range for V_(F) to the left ofthe slash and the range for V*_(F) to the right of the slash. For thevoltage configuration shown in FIG. 3A only pixels 34 in activatedregion 60 of photosensor 32 generate and store photocharge responsive toincident light. The active region may be moved and reconfigured bychanging the pattern of voltages applied to the column and row controllines.

In the description and claims of the present application, each of theverbs, “comprise” “include” and “have”, and conjugates thereof, are usedto indicate that the object or objects of the verb are not necessarily acomplete listing of components, elements or parts of the subject orsubjects of the verb.

Descriptions of embodiments of the disclosure in the present applicationare provided by way of example and are not intended to limit the scopeof the disclosure. The described embodiments comprise differentfeatures, not all of which are required in all embodiments. Someembodiments utilize only some of the features or possible combinationsof the features. Variations of embodiments of the disclosure that aredescribed, and embodiments comprising different combinations of featuresnoted in the described embodiments, will occur to persons of the art.The scope of the invention is limited only by the claims.

1. An active illumination range camera operable to determine distancesto features in a scene, the range camera comprising: an imaging systemcharacterized by a field of view (FOV) and comprising a photosensorhaving light sensitive pixels, and an optical system configured tocollect light from a scene in the FOV and image the collected light ontopixels of the photosensor; an illumination system controllable togenerate and direct a field of illumination (FOI) to illuminate at leasta portion of the FOV; and a controller operable to: partition the atleast a portion of the FOV into a plurality of zones; control theillumination system to generate and direct a FOI to sequentiallyilluminate the zones in turn and thereby features of the scene withinthe zones; based at least in part on a given zone being illuminated bylight transmitted in the FOI, activate pixels in a corresponding regionof the photosensor on which the imaging system images light from thefeatures in the zone to accumulate photocharge responsive to lightreflected by the features from the transmitted light, and inactivatepixels on which light from the features is not imaged; and determine anduse data based on the photocharge accumulated by the pixels to determinedistances to features in the scene and provide a range image for thescene.
 2. The active illumination range camera according to claim 1wherein sequentially illuminating the zones in turn comprisesilluminating each zone a plurality of times to acquire data sufficientto determine distances to features of the scene in the zone beforeilluminating a next zone.
 3. The active illumination range cameraaccording to claim 2 wherein the controller is operable followingillumination of each zone the plurality of times to read out the pixelsin the corresponding region.
 4. The active illumination range cameraaccording to claim 3 wherein using data comprises providing a rangeimage of the features in each zone and stitching the provided rangeimages to provide a range image of the scene.
 5. The active illuminationrange camera according to claim 1 wherein sequentially illuminating thezones in turn comprises: (a) illuminating each zone once in sequence toaccumulate photocharge to acquire a portion of the data for providing arange image of the scene; (b) repeating (a) a number of time sufficientto acquire all the data for providing the range image.
 6. The activeillumination range camera according to claim 5 wherein the controller isoperable following illumination of a zone to store photochargeaccumulated by pixels in the photosensor region corresponding to thezone in the pixels.
 7. The active illumination range camera according toclaim 6 wherein the controller is operable upon completion of eachrepetition, to read the photosensor to acquire a frame of thephotosensor.
 8. The active illumination range camera according to claim7 wherein the controller is operable to using data in all the frames toprovide a range image of the scene following a last acquisition of aframe.
 9. The active illumination range camera according to claim 6 andcomprising reading the pixels in the region to acquire a frame of theregion prior to illuminating a next region of the photosensor.
 10. Theactive illumination range camera according to claim 1 whereinpartitioning the FOV into zones comprises determining a number of zones.11. The active illumination range camera according to claim 10 whereindetermining a number of the zones comprises determining the number basedon reflectance of features in the FOV.
 12. The active illumination rangecamera according to claim 1 wherein the controller is operable tocontrol intensity of light in the FOI illuminating a zone and/orduration of exposure of the zone to the light based on reflectance offeatures in the zone.
 13. The active illumination range camera accordingto claim 1 and comprising at least one or any combination of more thanone of a continuous wave time of flight (CW-TOF) camera, a gated time offlight (GT-TOF) camera, a structured light range camera, and/or a stereorange camera.
 14. The active illumination range camera according toclaim 1 and comprising: controlling the illumination system to generateand direct a FOI that illuminates a zone with time modulated lightcharacterized by a modulation frequency; and differentially timemodulating sensitivity to light of pixels in the corresponding region ofthe photosensor at the modulation frequency of the modulated light butphase shifted from a phase of modulation of the light by an offsetphase.
 15. A method for determining distances to features in a scene,the method comprising: partitioning a field of view (FOV) of a camera inwhich the scene is located into a plurality of zones; generating anddirecting a field of illumination of a light source (FOI) tosequentially illuminate the zones in turn and thereby features of thescene within the zones; based at least in part on a given zone beingilluminated by light transmitted in the FOI, activating pixels in acorresponding region of the photosensor on which the camera images lightfrom the features in the zone to accumulate photocharge responsive tolight reflected by the features from the transmitted light, andinactivating pixels of the photosensor on which light from the featuresis not imaged; and using data based on the photocharge accumulated bythe pixels to determine distances to features in the scene and provide arange image for the scene.
 16. The method according to claim 15 whereinsequentially illuminating the zones in turn comprises illuminating eachzone a plurality of times to acquire data sufficient to determinedistances to features of the scene in the zone before illuminating anext zone.
 17. The method according to claim 16 and followingillumination each zone the plurality of times reading out the pixels inthe corresponding region.
 18. The method according to claim 17 whereinusing data comprises providing a range image of the features in eachzone and stitching the range images to provide a range image of thescene.
 19. The method according to claim 15 wherein sequentiallyilluminating the zones in turn comprises: (a) illuminating each zoneonce in sequence to accumulate photocharge to acquire a portion of thedata for providing a range image of the scene; (b) repeating (a) anumber of times sufficient to acquire all the data for providing therange image.
 20. The method according to claim 19 and comprising:following illumination of a zone storing photocharge accumulated bypixels in the photosensor region corresponding to the zone in thepixels; and upon completion of each repetition, reading the photosensorto acquire a frame of the photosensor; and following completion ofrepetition last repetition using data in all the frames to provide arange image of the scene.